260 THE ILLINOIS GLACIAL LOBE. 



chain leading from the river to the point of junction with the inner ridge. 

 The inner ridge has not such a crest but, instead, a gentle swell-and-sag 

 topography, with undulations of 20 to 25 feet. 



At the east branch of the Illinois- Vermilion River this morainic belt is 

 interrupted by a plain nearly 2 miles in width. The ridges are, however, 

 both present north of the river. The outer one appears in sees. 33 and 34, 

 Owego Township, and bears slightly west of north to Cayuga. The inner 

 appears in sec. 31, Saunemin Township, and bears northward about 2 miles, 

 and is interrupted by a gap through which Felkey Creek has its passage. 

 It appears on the west side of this creek and bears northwestward, joining 

 the outer one near Cayuga. Each of these ridges has a gently undulating 

 surface, but upon becoming coalesced a sharply imdulatory topography 

 sets in, in which the swells stand 30 to 40 feet above the bordering sags 

 and sloughs. 



From Cayuga northwestward to northern Livingston County the 

 moraine under discussion is so closely associated on the inner border with 

 the Marseilles moraine as to be obscured by it, and is interrupted by sev- 

 eral gaps where creeks tributary to the Illinois- Vermilion River traverse it. 

 These gaps occur at the following streams: Wolf Creek, Deer Creek, 

 Baker's Run, Mud Creek, and Blackstone Creek. The gaps are a mile or 

 less in width, while the ridges which lie between them occupy a length of 2 

 or 3 miles. These interrupted ridges consist of a series of billows ranging 

 in height from 10 feet up to 40 feet or more. The most prominent one 

 noted is in sec. 18, T. 30, R. 5 E., and is known as "Smith's Mound." It 

 occupies about 40 acres and stands nearly 50 feet above the surrounding 

 country. Basins occur on its summit. 



Farm Ridge or Grand Ridge. — In southern Lasalle County, just east of Streator, 

 as noted above, a morainic ridge known as Farm Ridge and also as Grand 

 Ridge emerges from the outer border of the Marseilles moraine. It appears 

 to be the continuation of the Chatsworth-Cayuga Ridg-e. For a few miles, 

 to Otter Creek Valley, it is separated from the Marseilles moraine by a 

 narrow valley-like plain scarcely a mile in width. In sees. 29 and 30, 

 T. 31, R. 4 E., it carries sharp knolls, but the remainder of the ridge in 

 the interval between the county line and Otter Creek has a gentty undu- 

 lating surface. At Otter Creek there is a break a mile or so in width. 



